N-heptane burning: Kinetic mechanism parameters
 

Hello!

I'm modeling one-step n-heptane combustion.

C7H16 + 11O2 -> 7CO2 + 8H2O

Does somebody know what are the units and values of pre-exponential factor and activation energy? Rate coefficients also wellcomed :)

Regards,

Julie

Re: N-heptane burning: Kinetic mechanism parameter
 

Remember that STAR-CD uses seconds, meters, kilograms and Joules for the units. Concerning your question, take a look to the methodology guide page 10-4. Remember that the scalars are mass fractions (and no concentrations defined as volumetric fractions -- with the exception of the VOF scalar), so the scalar unit is [kg/kg]. Hope this helps.

The answer
 

This is the answer I got from the support:

It is good practice to be consistent with units when inputting data. To this end I would recommend ensuring that the value you use for Activation energy is in j/kg-mol and that the value for the pre-exponential factor (A) is consistent with SI units (i.e. units of reaction rate are kg/m3-s). I am not sure if the values you quote are reasonable but I have attached some values in SI units for the combustion of n-heptane in air that you may wish to compare with your own data:

Pre-exponential Factor: 2.868e+9

Activation Energy: 1.256e+8 (j/kg-mol)

Rate Exponent (a): 0.25

Rate Exponent (b): 1.5

Re: N-heptane burning: Kinetic mechanism parameter
 

The activation energy has units of Kcal/kmolK but you might change the Kcal units to joules since STARCD uses the international system of units